Distinct Configurations of Cations and Water in the Selective Filter of the KcsA Potasium Channel Probed by the 3D-RISM Theory
Distinct Configurations of Cations and Water in the Selective Filter of the KcsA Potasium Channel Probed by the 3D-RISM Theory
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3D-RISM 理论探测 KcsA 钾通道选择性过滤器中阳离子和水的不同构型
DOI：
10.1016/j.molliq.2014.03.050
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
and Fumio Hirata
中科院分区：
文献类型：
--
作者：
Saree Phongphanphanee;Norio Yoshida;Shigetoshi Oiki;and Fumio Hirata
钾离子通道对K+的选择性高于其他一价阳离子，并且直径为3 μ m的窄孔结构称为选择性过滤器（SF）负责选择性渗透。在这里，我们应用的统计力学的液体称为三维参考相互作用网站模型（3D-RISM）理论，和一价阳离子，Li+，Na+和K+的结合配置，特别注意水的贡献在KcsA钾通道进行了检查。所有这三种类型的阳离子结合在开放的SF具有高亲和力，但具有不同的结合配位：笼内配置由八个羰基氧为K+，和平面内配置由四个羰基氧为Li+，而这两种配置都允许Na+。在每种情况下，水都是离子配位的组成部分。在Li+的情况下，线性水-Li +-水络合物被安置到两个相邻的笼中，Li+以面内位点为中心。Na+周围的水的位置更灵活，这可以允许平面内和笼内配置之间的过渡。K+稳定占据笼内构型，水占据相邻笼。这些结果提供了SF中离子和水的独特构型，并为选择性的基本过程提供了线索。
The potassium channel is highly selective for K+over other monovalent cations, and the narrow pore structure with 3 Å in diameter named the selectivity filter (SF) is responsible for the selective permeation. Here we applied the statistical mechanics of liquids called three-dimensional reference interaction site model (3D-RISM) theory, and the binding configurations of the monovalent cations, Li+, Na+and K+, with special attention on the contribution of water in the KcsA potassium channel were examined. All the three types of cations are bound in the open SF with high affinity, but with different binding coordinations: the in-cage configuration by eight carbonyl oxygens for K+, and the in-plane configuration by four carbonyl oxygens for Li+, whereas both configurations are allowed for Na+. In each case, water contributes an integral part of the ion coordination. In the case of Li+, a linear water-Li+-water complex is settled into two adjacent cages with the Li+centered at the in-plane site. Positions of water around Na+are more flexible, which may allow a transition between in-plane and in-cage configurations. K+stably occupied in-cage configuration, and water occupies adjacent cages. The results provide the distinct configuration of ion and water in the SF, and serves clues for elementary process of selectivity.